Understanding translation at the molecular level depends upon understanding the three-dimensional structure of the ribosome. The purpose of this proposal is to map the three-dimensional proximities between 16S rRNA and specific sites within certain 30S ribosomal proteins. A modification of hydroxyl radical cleavage, using tethered Fe(II)-EDTA, will generate an extensive set of unambiguous constraints for the folding of 16S rRNA in a fully reconstituted 30S ribosomal subunit.